<!DOCTYPE html>
<html>
<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <style>
    
  </style>
</head>
<body>
  
</body>
<script>

  console.log(NaN === NaN);
  console.log(NaN == NaN);

  console.log(typeof NaN);

  console.log( isNaN( NaN ) );
  console.log( isNaN( 365 ) );
  
  console.log( isNaN( "hello" ) );

  console.log( isNaN( "365" ) );
  
  console.log( isNaN( "365a" ) );
  
</script>
</html>